Function getrand

src/bin/pgbench/pgbench.c:931–944

* Random number generator: uniform distribution from min to max inclusive. * * Although the limits are expressed as int64, you can't generate the full * int64 range in one call, because the difference of the limits mustn't * overflow int64. In practice it's unwise to ask for more than an int32 * range, because of the limited precision of pg_erand48(). */

 * range, because of the limited precision of pg_erand48().
 */
static int64
getrand(RandomState *random_state, int64 min, int64 max)
{
	/*
	 * Odd coding is so that min and max have approximately the same chance of
	 * being selected as do numbers between them.
	 *
	 * pg_erand48() is thread-safe and concurrent, which is why we use it
	 * rather than random(), which in glibc is non-reentrant, and therefore
	 * protected by a mutex, and therefore a bottleneck on machines with many
	 * CPUs.
	 */
	return min + (int64) ((max - min + 1) * pg_erand48(random_state->xseed));
}

/*
 * random number generator: exponential distribution from min to max inclusive.